The present invention relates generally to the field of electrical rotating machines, such as motors, generators, or the like. More particularly, the present techniques concern the control of such rotating machines.
Electrical rotating machines, such as electric motors, generators, and other similar devices, are quite common and may be found in diverse industrial, commercial, and consumer settings. These machines are produced in a variety of mechanical and electrical configurations. The configuration of these devices may depend upon the intended application, the operating environment, the available power source, or other similar factors. In general, these devices include a rotor surrounded at least partially by a stator.
For instance, one common design of electrical rotating machine is the induction motor, which is used in numerous and diverse applications. In industry, such motors are employed to drive various kinds of machinery, such as pumps, conveyors, compressors, fans and so forth, to mention only a few. Conventional alternating current (AC) electric induction motors may be constructed for single-phase or multiple-phase power and are typically designed to operate at predetermined speeds or revolutions per minute (rpm), such as 3600 rpm, 1800 rpm, 1200 rpm, and so forth.
Control schemes are often used to automate electromechanical systems having the foregoing electrical rotating machines. For example, an assembly of power and data wires may connect the electrical rotating machine, sensors, and other components to a central control unit. The central control unit generally receives sensor data and user input, processes the data, and then distributes commands to the various components including the electrical rotating machine. In other words, the central control unit is the brains of the system, while the components merely receive and respond to the commands. As appreciated, extensive wiring, connectors, and response time are particularly influential on the cost, performance, reliability, and safety of the system. Unfortunately, many industrial and commercial systems are spread out over a very large area, which requires long runs of data wires to the components, sensors, and so forth. This results in increased costs and less reliability of the system. This also results in a significant time delay between the time an event occurs in the system and the time that the central control unit subsequently responds to the event. In other words, the sensor feedback may be transmitted in a raw form along a long length of wire to the central control unit, which then processes the raw sensor feedback and provides a control signal to the appropriate components. Again, the control signal may be transmitted along another long length of wire to the appropriate components. These delays can drastically reduce the overall performance of the system.